Snack foods have traditionally been manufactured from raw materials having a base either of potatoes (fresh, sliced or dehydrated) or corn. Corn snacks are either sheeted or extruded into a flat planar configuration (tortilla chips) or into various shapes depending upon extruder die design. Corn is typically prepared for inclusion in snack foods by either preparing a limed masa for a traditional Mexican flavor, or by simply cooking the corn without lime to avoid the Mexican flavor.
The most common method of preparing corn masa is to grind the cooked corn kernels in a stone grinder. Such stone grinders consist of a pair of cylindrical stones having radially fluted faces, with one stone stationary and the other rotating. Cooked corn is fed through an opening in the center of the stationary stone by an auger, and is ground as it is forced radially outwardly along the radial flute. Manufacturers of corn masa have recognized for many years that the production of acceptable masa is an art, not a science. Typically, an operator of a stone grinder having many years experience simply "feels" the ground corn exiting the stone grinder to determine whether or not it is acceptable. No empirical tests are used in the industry to determine whether or not an acceptable grind is occurring. Rather, if the ground corn exiting the stone grinders is too coarse to the feel, the operator simply reduces the gap between the stones; conversely, if the corn exiting the grinders is too fine, the operator increases the gap between the stones.
While the art of stone grinding corn is quite subjective, the results of a ground corn being too coarse or too finely ground can be dramatic. Fried snack foods made from coarsely ground corn have a grainy, sandy texture, and because of the coarse grinding, the snacks are crumbly and do not hold together well. Snacks made from corn too finely ground form a very dense, hard product which is unpleasantly brittle. Therefore, the correct grind on the corn masa is critical to manufacturing a consistent corn snack having acceptable organoleptic properties.
The grinding action of stone grinders tends to produce a relatively high proportion of "fines" in the ground corn. As used herein, the word "fines" means corn particles capable of passing through a U.S. #80 mesh screen (having an aperture diameter of 0.177 mm). As noted above, fines tend to produce a hard, dense, brittle product. In U.S. Pat. No. 4,803,091, issued Feb. 7, 1989, a process is disclosed for the manufacture of fried corn snacks wherein limed corn is produced by a combination of stone grinding followed by grating/cutting in a cutting mill, such as an Urschel Comitrol mill. The ground corn is incorporated into a dough, which is extruded in a spiral ribbon, subsequently cut into individual pieces and fried.
Manufacturers of fried masa-based corn snacks generally rely upon the natural expansion of the masa to effect the final product characteristics. However, because stone grinding produces a variable level of fines, expansion of corn snacks is often greater or less than optimal, resulting in a product having unpredictable organoleptic properties, such as taste, texture, grittiness or hardness. Consumers have come to accept these attributes as representative of fried masa-based corn snacks.
Therefore, it is an object of the present invention to produce a masa-based fried corn snack having an expanded, less dense texture resulting from the inclusion of fewer fines in the dough. Additionally, ingredients added to the dough to induce additional expansion of the dough during frying are contemplated. Finally, it is an object cf the present invention to provide a process whereby corn masa having a reasonably consistent particle size distribution can be produced, so that products having known attributes can be designed.